1. Technical Field
The present invention relates to an image forming apparatus, an image processing method, and a control software program of an image forming apparatus, and more particularly to control of a background pattern printing to enhance security of output sheets.
2. Description of the Background Art
With the advancement of information digitization, image processing apparatuses such as printers or facsimile machines for outputting digitized information and scanners for digitizing document information have become indispensible apparatuses. Such image processing apparatuses have image capturing, image forming, and communication capabilities, which enable them to function as printers, facsimiles, scanners, copiers, or multi-functional apparatuses combining several of these capabilities and known as multi-functional peripherals (MFP).
Among such image processing apparatuses, there are printers for outputting digitized information that employ a background pattern printing technique that superimposes specific dot patterns or image patterns on printed images to prevent forgery and information leak. Depending on the specific pattern formed on the sheets, these patterns can be detected when someone tries to copy such sheets using certain types of equipment, and prohibits such copying.
Further, even if such sheets are copied by generally available image forming apparatuses, specific patterns such as text strings may appear on the copied sheets due to the difference in recognition level of the specific patterns with respect to other portion. Therefore, such copied sheets can be instantly recognized as copied documents, by which unauthorized copying can be prevented.
Such background pattern printing may be suitably conducted for each printing operation even when different users conduct printing operations. Thus, for example, JP-2007-179532-A discloses a method of determining a suitable content of a background pattern to be superimposed for print jobs to be conducted by different users.
Such background pattern printing can be reliably conducted as follows: Firstly, an image forming apparatus is required to superimpose a background pattern to a print job input to the image forming apparatus, and secondly, the superimposing setting can be changed only by an administrator or the like that has a higher access right. In such a case, general users having limited access right cannot change the settings of the background pattern printing, and cannot change the text strings superimposed as a background pattern. If the limited access right users can change the settings freely, some users may cancel the background pattern printing, by which the background pattern printing is not conducted.
The background pattern printing may be used differently for in-house documents and public documents. For example, text strings superimposed as background pattern may be changed for an in-house document and a public document, such as “NO COPY” for the in-house document, and an outputting date and a name of an output person for the public document.
However, if only the administrator having a higher access right can change the background pattern conditions as described above, such condition change in view of each distribution destination cannot be conducted by general users having limited access right. If the general users want to change the conditions, the general users need to request such change to the administrator each time a document is printed, which is inconvenient.